Summary a,b-Diamino acids are widely popular recent years as to the bio-active property and key position in synthetic methods. Among the various approaches for a,b-diamino derivatives, Mannich reaction of a-isothiocyanato imides shows it’s key position in it.
As a bifunctional catalyst, guanidine catalyzes asymmetric Mannich reaction well. And chiral bisguanidine showed better results than normal monoguanidine. The stereo chemistry is preferred to tosyl group andCHCl3 as solvents.
By using achiral additives of weak acids to the reaction system, the enantioselectivity had improved. And sulfonyl group played a key role of the stereoselectivity, which the functional group with a sulfonyl group gave as much a as 92% ee, while the mesyl group gave only 65% ee.
Under the optimized conditions, various imines were investigated for the reaction. And aldimine substrates showed the best results . At last, the author elaborated the mechanism of the reaction and gave the practical way to scale-up production.
In the final, the author summarized the novel catalyst used for the Mannich-type reaction and gave the experimental part.
Reference: Xiaohong Chen, Shunxi Dong, Zhen Qiao, Yin Zhu, Mingsheng Xie, Lili Lin, Xiaohua Liu*, Xiaoming Feng*, Guanidine Organocatalyst for the Asymmetric Mannich-Type Reaction between - Isothiocyanato Imide and Sulfonyl Imines, Chem. Eur. J., 2011, 17, 2583-6
a,b-Diamino acids are widely popular recent years as to the bio-active property and key position in synthetic methods. Among the various approaches for a,b-diamino derivatives, Mannich reaction of a-isothiocyanato imides shows it’s key position in it.
As a bifunctional catalyst, guanidine catalyzes asymmetric Mannich reaction well. And chiral bisguanidine showed better results than normal monoguanidine. The stereo chemistry is preferred to tosyl group andCHCl3 as solvents.
By using achiral additives of weak acids to the reaction system, the enantioselectivity had improved. And sulfonyl group played a key role of the stereoselectivity, which the functional group with a sulfonyl group gave as much a as 92% ee, while the mesyl group gave only 65% ee.
Under the optimized conditions, various imines were investigated for the reaction. And aldimine substrates showed the best results
.
At last, the author elaborated the mechanism of the reaction and gave the practical way to scale-up production.
In the final, the author summarized the novel catalyst used for the Mannich-type reaction and gave the experimental part.
Reference:
Xiaohong Chen, Shunxi Dong, Zhen Qiao, Yin Zhu, Mingsheng Xie, Lili Lin, Xiaohua Liu*, Xiaoming Feng*, Guanidine Organocatalyst for the Asymmetric Mannich-Type Reaction between - Isothiocyanato Imide and Sulfonyl Imines, Chem. Eur. J., 2011, 17, 2583-6
DOI: dx.doi.org/10.1002/chem.201002571